Foamed glass composite material and a method for using the same

ABSTRACT

A method of slowing an aircraft overrunning a runway, including paving an area immediately beyond the end of a runway with foamed glass bodies to define a bed, covering the bed with a layer of cementitious material to define a composite bed, and crushing at least a portion of the composite bed with an oncoming aircraft, wherein crushing the at least a portion of the composite bed removes kinetic energy from the oncoming aircraft to slow the oncoming aircraft. The composite bed is generally resistant to fire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to co-pending U.S. patentapplication Ser. No. 11/276,193 filed on Feb. 17, 2006, and to U.S. CIPpatent application Ser. No. 14/301,988, filed on Jun. 11, 2014.

TECHNICAL FIELD

The invention relates generally to the field of ceramic compositematerials and, specifically, to a composite ceramic material having atailored failure mode and including a lightweight foamed glass or foamedsilaceous slag portion and a cemetitious, concrete, gypsum or otherceramic portion, and method of using the same.

BACKGROUND

Foamed glass is an established lightweight ceramic material. Typically,foamed glass is made in one of two ways. The first way involvespreparing a stable foam from water and foaming agent, preparing a wetmixture or slurry of solid components (where cement is the mainsubstance), quick mixing the foam and the slurry, filling molds withprepared the mixed foam/slurry, and firing the same. The second way tomake foamed glass involves making use of the property of some materialsto evolve a gas when heated. A foamed glass material may be prepared bymixing crushed vitreous particles and a foaming agent (such as CaCO₃ orCaSO₄), placing the mixture in a mold, heating the mold (such as bypassing the mold through a furnace) to a foaming temperature, andcooling the mold to produce foamed glass bodies.

Slag is a nonmetallic byproduct of metallurgical operations. Slagstypically consist of calcium, magnesium, and aluminum silicates invarious combinations. Iron and steel slags are byproducts of iron andsteel production. For example, an iron blast furnace is typicallycharged with iron ore, fluxing agents (such as limestone or dolomite)and coke (as fuel and reducing agent). Iron ore is typically a mixtureof iron oxides, silica, and alumina. When sufficiently heated, moltenslag and iron are produced. Upon separation of the iron, the slag isleft over. The slag occurs as a molten liquid melt and is a complexsolution of silicates and oxides that solidifies upon cooling.

The physical properties of the slag, such as its density, porosity, meanparticle size, particle size distribution, and the like are affected byboth its chemical composition and the rate at which it was cooled. Thetypes of slag produced may thus conveniently be classified according tothe cooling method used to produce them—air cooled, expanded, andgranulated. Each type of slag has different properties and, thus,different applications.

While useful as insulation and as abrasive materials, foamed glassbodies (made with or without foamed slag), are typically unsuitable foruse as lightweight filler and/or in composite materials due to factorsincluding cost and the propensity for foamed glass to hydrate andexpand.

Thus, there remains a need for an easily produced foamed glass materialthat is more resistant to expansion from hydration and/or more easilyaged, and for composite materials incorporating the same. The presentinvention addresses this need.

SUMMARY

The technology discussed below relates to manufactured compositematerials, such as roadbed and airport runway safety areas (RSA's)incorporating lightweight foamed glass and cementitious or other ceramicmaterials to define structural composite materials having controlledfailure mode properties, and the method for making the same. One objectof the present invention is to provide an improved foamedglass-containing structural composite RSA material. Related objects andadvantages of the present invention will be apparent from the followingdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a first embodiment of a process for makingfoamed glass composites.

FIG. 2A is a schematic view of a second embodiment of a process formaking foamed glass bodies and composites and its uses.

FIG. 2B is a schematic view of a third embodiment of a process formaking foamed glass bodies and composites and its uses.

FIG. 3A is a schematic view of a process for mixing a batch ofprecursors for a foamed glass article according to a fourth embodimentof the present novel technology.

FIG. 3B is a schematic view of a process for firing a foamed glassarticle mixed according to FIG. 3A.

FIG. 3C is a perspective view of as milled glass powder according to theprocess of FIG. 3B.

FIG. 3D is a perspective view of rows of milled glass powder mixtureready for firing.

FIG. 3E is a perspective view of FIG. 3D after firing into asubstantially continuous foamed glass sheet.

FIG. 4 is a process diagram of the process illustrated in FIGS. 3A and3B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theclaimed technology and presenting its currently understood best mode ofoperation, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, with such alterations and furthermodifications in the illustrated device and such further applications ofthe principles of the claimed technology as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe claimed technology relates.

Vitreous materials, such as soda-lime-silica glasses and metallurgicalbyproduct slags, are typically foamed through a gasification processesto yield a typically predominately vitreous, typically silaceousresultant cellular product. Typically, a foaming precursor ispredominately vitreous or non-crystalline prior to the foaming process,since a glassy precursor slag material typically has a viscosity attemperature that is convenient to the foaming process. More typically,the vitreous starting material will have a traditional soda-lime-silicaglass composition, but other compositions, such as aluminosilicateglasses, borosilicate glasses, vitreous peralkaline slag or othervitreous slag compositions may be foamed as well. For example, aperaluminous slag with significant alkali and alkaline earth oxides mayalso be utilized. After the vitreous precursor is foamed, the foamedglass is physically combined with cement to form a composite materialsuitable for building or structural applications or the like.

In the case of slagaceous precursor materials, the slag is typicallypredominately vitreous in character, and more typically has a maximum40% by volume crystalline material. The slag is typically initiallycrushed and sized to approximately 10 microns median particle size, moretypically at least 90 percent of all particles are less than 75 microns.

If the crushed and/or powdered slag is dry, water is added to thepowdered slag to about 0.1 to about 0.5% (by mass). Alternately, if nowater is added, limestone or other solid foaming agent may be added(typically about 4 percent or less by mass, more typically about 2percent or less by mass). The mixture is then formed into pellets(between 0.05 and 1 cubic centimeter), preheated (to no more than within25° C. of the dilatometric softening point) and then passed through ahigh temperature zone, such as one generated by a rotary kiln or a flame(contained in a ceramic or refractory metal tube). The residence time inthe zone is short, typically about 0.5 to about 10 seconds, and thetemperature is high (adiabatic flame temperature in excess of 1300° C.).In the case of a flame, the thermal energy provided to the material bythe direct flame enables a change of state reaction in the foaming agentand the resulting gas will force the now viscous matter to foam. Thefoamed pellets or foamed media are air quenched below the dilatometricsoftening point of the material, and then allowed to dry by slowcooling.

The foamed media typically have a relative volume expansion in excess ofthree fold, and more typically the volume expansion is as high as 10fold or greater. This process results in individual, low-density(specific gravity less than 0.3) foamed media with a median pore size inthe range of 0.1 to 2 mm.

Composite materials may be prepared by mixing the foamed slag withPortland cement; at least two types of composite materials may be madeaccording to this technique. A first composite material may be preparedby mixing a thin mixture of cement with foamed media, wherein the foamedmedia comprises at least 85 volume percent of the total cement/otheraggregate. The foamed media are typically incorporated into the cement(and aggregates, if needed) after the water has been added. Theresulting mixture acts as a very viscous material and is pressure orgravity formed into a slab (or other coherent shape) or direct cast intoa prefabricated form. The shape or form is then allowed to set. Theresulting composite material sets up to be a rigid, relativelylightweight (specific gravity <0.75) material with surface propertiestypical of Portland cements. Chemicals and finishing systems compatiblewith Portland cement can be used in conjunction with this material.

A second composite material is formed as a mixture of cement withtypically less than 50 volume percent foamed slag media. The media istypically dry mixed with cement prior to water additions. The mixture isthen prepared as common cement. Additional aggregates may beincorporated as per common practice. This second composite material hasa very high strength; the composite compressive strength is typically atleast 25% higher per unit mass than is that of the identical cementprepared without the foamed slag addition. It can be used in anyapplication compatible with Portland cement.

A third composite material is formed as aqueous slurry mixture comprisedof gypsum with typically less than 50 percent by volume foamed glass orslag. The media are typically added to the gypsum after the material isslurried. Additional binders, fillers and setting agents may be addedper common practice. The resulting material has a very low density andhigh acoustic absorption. There are no chemical compatibilitylimitations on the extent of foamed glass additions. Any limitationstypically arise from strength considerations and other physicalproperties.

In another example, the vitreous precursors 210 to the foaming processare waste glasses. Waste glasses typically have a soda-lime-silicacomposition, and are generally first crushed or ground 220, and thentypically sized 230, to produce a particulate frit 235 suitable forpelletizing 250 or otherwise forming into regular shapes for foaming.

As with slagaceous precursors as described above, if the particulatewaste glass 210 is dry, water may be added to the in small amounts topromote handling and to better adhere the foaming agent uniformly to theparticles for more even distribution. Alternately, if no water is added,limestone or other solid foaming agent 240 may still be added, typicallyin small amounts (such as less than 2 percent by mass) and mixed to forma substantially heterogeneous foamable vitreous mixture. The mixture 245is then typically formed 250 into pellets (between 0.05 and 1 cubiccentimeter), loaves, or other regular green bodies 260 convenient forfoaming and is next preheated 265, typically to no more than within 25°C. of the dilatometric softening point. Preheating 265 readies the greenbodies 260 for rapid heating 270 into the foaming temperature region.

The preheated green bodies 260 are then passed through a hightemperature zone 275, such as one generated by a rotary kiln or a flame(contained in a ceramic or refractory metal tube). The residence time inthe zone is short, typically about 0.5 to about 10 seconds, but may belonger for larger green bodies 260. The temperature is substantiallyhigh (adiabatic flame temperature at least about 1200° C. and typicallyaround 1300° C. or higher). The rapid influx of thermal energy providedto the material enables a change of state reaction in the foaming agent240 and the resulting gas will force the now viscous matter to foam.

The foamed bodies 275 are then rapidly quenched 280 to below thedilatometric softening point of the material, and then allowed to coolto room temperature at a second, typically slower, cooling rate. Thecooling rate is typically rapid enough such that the foamed glass 275does not anneal or only partially anneals, resulting in a harder foamedglass body 285 with built-in stresses that enhance its crushing strengthand toughness, and also give rise to a crushing failure mode incompression and torsion. The cooling rate typically varies due to beltspeed. The high end is typically about 15-25° C. per minute, while thelow end is typically about 10-20° C. per minute for the temperaturerange from the foaming temperature to just below the dilatometricsoftening point; more typically, cooling from the foaming temperature tobelow the dilatometric softening pint temperature occurs at a rate ofabout 20 degrees Celsius per minute. The cooling rate typicallydiminishes as the body 285 approaches the softening point.

After foaming, the bodies 275 leave the kiln and are quenched 280,typically via exposure to air or forced water jacket cooling, and thecooling rate is increased to about 25-40° C. per minute during the rapidquench, more typically at least about 30 degrees Celsius per minute.After the rapid quench, the cooling rate is decreased to about 3-10° C.per minute. All cooling rate values are for the center of the foamedglass bodies 285.

For foamed media produced on a belt process, the pellets or green bodies260 are typically configured such that the resultant foamed glass bodies275, 285 have irregular oblong or ovoid shapes. More typically, thegreen bodies 260 are preformed or pressed pellets sized such that theresultant foamed bodies 275, 285 have major axis dimensions of betweenabout 10 mm and 80 mm. Accordingly, these bodies 285 are typically sizedand shaped to be engineered drop-in replacements for mined gravelaggregate and have superior water management, compressive strength,failure mode, erosion, stackability, chemical stability and toughnessproperties. Alternately, the foamed bodies 285 may be made to otherconvenient size and shape specifications, such as in larger orthorhombicparallelepiped or ‘brick’ shapes, still larger ‘cinder block’dimensions, relatively thin plates, and the like.

One advantage of this process is that the furnace residence time ofvitreous bodies 275 during the foaming process is reduced a factor of4-9 over most conventional glass foaming techniques. Moreover, thefoamed glass bodies 285 can be produced with mean cell sizes of lessthan about 0.2 mm in diameter, and with typically individual cells sizesranging down to about 0.1 mm in diameter or less. Bodies 285 having suchsmall cell sizes are typically of the closed cell type, which gives riseto crushing strengths of well over the typical 100 psi (for comparablydense open cell material) to well over 200 psi. Further, bodies 285having substantially open cells sized in the less than 0.1-0.2 mm rangeexhibit enhanced capillary action and accordingly rapidly absorb andefficiently retain water.

The natural break-up of the material under rapid cool down, due tothermally induced stresses, results in a more angular, jagged foamedglass body 285 as opposed to a foamed glass piece shaped by crushing alarge body. The physical measure is that the so-produced foamed glassbodies 285 have a range of aspect ratios (largest to smallest diameter)about 50% higher than the 1 to 1.25 ratio average for smaller bodiesformed via a crushing process. This gives rise to the 35 degree stackingangle and ensures the material breaks up before slip failure.

In one example, oblong, irregularly shaped foamed bodies 285 produced asdescribed above and having major axial dimensions of about 80 mm areused as fill material 290 behind rock retaining walls. As these fillmaterial bodies are relatively light weight, relatively strong incompression, have a characteristic stacking angle of about 35 degreesand are characterized by an open pore structure, a substantially smallervolume of foamed glass aggregate fill is required as compared totraditional mined gravel. For a 6 foot retaining rock wall, the requiredfoundation thickness is reduced from 54 inches to 24 inches, therequired rock is reduced by 7.5 cubic feet per linear foot of wall, andthe required concrete is reduced by 2.5 cubic feet per linear foot ofwall. The amount of graded fill is reduced from 40 cubic feet per linearfoot of wall to 24 cubic feet per linear foot of wall. This reduction ismade possible by the high stacking angler (about 35 degrees) of thefoamed glass aggregate material 290, the physical manifestation of whichis its tendency to fail by a crushing mechanism (shattering of theindividual cells) instead of the individual aggregate pieces slidingover themselves. Additionally, the open pore structure of the foamedglass aggregate 285 gives rise to superior drainage and water managementproperties, reducing or eliminating the need for a separate inlaid drainpipe. In other words, by replacing mined gravel with engineered foamedglass aggregate 290 characterized by a high stacking angle, the amountof fill may be nearly halved and, consequently, the foundation depth andwall thickness may likewise be substantially reduced.

Likewise, the foamed glass aggregate fill may replace traditional minedfill gravel 295 in road beds. Less volume of the foamed glass aggregatefill is required, as it has superior strength, porosity and failure modecharacteristics, giving rise to shallower road beds, reducedconstruction time and expenses, less excavated dirt to be trucked away,reduced energy usage in road construction, simplified road drainage, andthe like. Moreover, the roads themselves may be constructed of concreteincluding foamed glass aggregate made as described above, which likewisehas enhanced strength and decreased weight characteristics.

In another embodiment, the foamed glass bodies produced as describedabove may be incorporated into acoustic ceiling tiles 300. The foamedglass material is chemically stable and inert, non-toxic, lightweight,and its porosity gives rise to sound-dampening. The tiles may be madeentirely of shaped foamed glass (in the form of relatively thin panels),or may incorporate foamed glass particles or bodies in a structuralmatrix, such as a polymer based, fibrous, cementitious, or like matrixmaterial. Of course, the foamed glass bodies 285 may also be used asaggregate 305 in traditional concrete.

In another embodiment, foamed glass bodies 285 are produced, in sometypical embodiments as described above, for incorporation into RSA's350. Typically, the foamed glass bodies are produced having a closedcell or closed porosity structure to prevent water infiltration andhydration. The foamed glass material is chemically stable and inert. TheRSA's 350 are typically formed from a foamed glass composite material360 including foamed glass bodies 295 in a ceramic matrix 370.Typically, the composite material includes at least about 50 volumepercent foamed glass, more typically at least about 60 volume percentfoamed glass, still more typically at least about 70 volume percentfoamed glass, yet more typically at least about 80 volume percent foamedglass, and in some embodiments at least about 90 volume percent foamedglass. The foamed glass bodies may be in the form of aggregate 305,shaped foamed glass blocks, or a combination of sizes and shapesincorporated into a structural matrix 370, such as a polymer based,fibrous, cementitious, or like matrix material. In some embodiments, thefoamed glass bodies 285 may also be used as aggregate 305 in traditionalconcrete. For RSA's, a higher relative volume of the foamed glassaggregate 305 and/or bodies 285 fill is required, as the composite RSA360 typically has lower crush strength to provide the desiredpredetermined failure mode characteristics, i.e., the RSA 360 will crushunder the weight of an oncoming aircraft to bleed off its kinetic energyand slow its progress across the RSA 360 until it stops. Moreover, theRSAs 360 are typically constructed of foamed glass bodies 285 and/oraggregate 305 (more typically closed cell foamed glass aggregate 305and/or bodies 285) in a thin ceramic or structural matrix 370, whereinthe surface 375 of the RSA 360 is matrix material 370. The matrix 370may be concrete, asphalt, or the like. The RSA 360 typically has a solidsurface 375, and more typically has a textured or contoured surface 375to further bleed kinetic energy from an oncoming aircraft.

The foamed glass bodies 285 for the RSA composite 360 may generally beprepared as described above, albeit the bodies 285 are typically foamedat a higher temperature, typically between about 1600 degrees Celsiusand about 1900 degrees Celsius, to yield a closed pore structure. Inother embodiments, the foamed glass may be prepared by the techniquesdescribed in U.S. Pat. Nos. 5,821,184 and 5,983,671, or the like.

FIGS. 3A-4 illustrate another method of producing lightweight foamedglass matrix 110 defining a plurality of voluminous, closed off and/orinterconnecting pores 115. The pores 115 typically have diametersranging from about 0.2 mm to about 2.0 mm. The pore walls 117 can beformed to exhibit a crazed or microcracked microstructure 119. Asillustrated schematically in FIGS. 3A-4, a ground, milled and/orpowdered glass precursor 120, such as recycled waste bottle and/orwindow glass, is mixed with a foaming agent 122 (typically a finelyground non-sulfur based gas evolving material, such as calciumcarbonate) to define an admixture 127. The foaming agent 122 istypically present in amounts between about 1 weight percent and about 3weight percent and sized in the average range of about 80 to minus 325mesh (i.e. any particles smaller than this will pass through—typically,the apertures in 80 mesh are between about 150 and about 200 micrometersacross and the apertures in −352 mesh are between about 40 and about 60micrometers across). More typically, the foaming agent has a particlesize between about 5 and about 150 microns. Typically, a pH modifiersuch as dicalcium phosphate 124 is added to the admixture 27, whereinthe pH modifier 124 becomes effective when the foamed glass product 110is used in an aqueous environment. The pH modifier 124 is typicallypresent in amounts between about 0.5 and 5 weight percent, moretypically between about 1 and about 2 weight percent. Additional plantgrowth nutrient material may be added to the starting mixture to vary orenhance the plant growth characteristic of the final product 110.

Foamed glass, like most ceramics, is naturally hydrophobic. Ashydrophobic surfaces are not conducive to wetting and impede capillaryaction, treatment is typically done to make the pore walls 117hydrophilic. In one embodiment, the pore walls 117 are coated to form aplurality of microcracks 119 therein. The microcracks 119 supplyincreased surface area to support wicking. Alternately, or in addition,an agent may be added to further amend the surface properties to makethe foamed glass more hydrophilic. Such an agent may be a large divalentcation contributor, such as ZnO, BaO, SrO or the like. The hydrophilicagent is typically added in small amounts, typically less than 1.5weight percent and more typically in amounts of about 0.1 weightpercent.

The combination is mixed 126, and the resulting dry mixture 127 may thenbe placed into a mold 128, pressed into a green body and fired withoutthe use of a mold, or, more typically, arrayed into rows 131 of powdermixture 127 for firing and foaming. Typically, whether placed 129 intothe mold 128 or not, the mixture 127 is typically arrayed in the form ofseveral rows 131, such as in mounds or piles of mixture typically havinga natural angle of repose of about 15 to 50 degrees, although evengreater angles to the horizontal can be achieved by compressing the drymixture 127. This arraying of the rows 131 allows increased control,equilibration and optimization of the heating of the powder 127 duringfiring, reducing hot and cold spots in the furnace as the powder 127 isheated. This combing of the powder 127 into typically rows 131 oftriangular cross-sections allows heat to be reflected and redirected tokeep heating of the rows generally constant.

The mold 128, if used, is typically a refractory material, such as asteel or ceramic, and is more typically made in the shape of a frustumso as to facilitate easy release of the final foamed glass substrate110. Typically, the inside surfaces of the mold 128 are coated with asoft refractory release agent to further facilitate separation of thefoam glass substrate 110 from the mold 128. In a continuous process, thepowder 127 is typically supported by a fiberglass mesh fleece or thelike to prevent fines from spilling as the powder 127 is moved viaconveyor through a tunnel kiln; the fleece is burned away as the powder127 sinters.

The so-loaded mold 128 is heated 130 in a furnace by either a batch orcontinuous foaming process. More typically, the mixture 127 is thenheated 130 in order to first dry 132, the sinter 134, fuse 136, soften138, and foam 140 the mixture 127 and thereby produce a foamed glasssubstrate 110 having a desired density, pore size and hardness. As thepowdered mixture 127 is heated to above the softening point of glass(approximately 1050 degrees Fahrenheit) the mixture 127 begins to soften138, sinter 134, and shrink. The division of the powdered mixture 127into rows or mounds allows the glass to absorb heat more rapidly and totherefore foam faster by reducing the ability of the foaming glass toinsulate itself. At approximately 1025 degrees Fahrenheit, the calciumcarbonate, if calcium carbonate has been used as the foaming agent 122,begins to react with some of the silicon dioxide in the glass 120 toproduce calcium silicate and evolved carbon dioxide. Carbon dioxide isalso evolved by decomposition of any remaining calcium carbonate oncethe mixture reaches about 1540 degrees Fahrenheit, above which calciumcarbonate breaks down into calcium oxide and carbon dioxide gas. Oncethe temperature of the mixture 127 reaches about 1450 degreesFahrenheit, the glass mixture 127 will have softened sufficiently forthe released carbon dioxide to expand and escape through the softened,viscous glass; this escape of carbon dioxide through the softened glassmass is primarily responsible for the formation of cells and porestherein. The mixture 127 in the mold 128 is held for a period of time ata peak foaming temperature of, for example, between about 1275 and about1900 degrees Fahrenheit, more typically between about 1550 and about1800 degrees Fahrenheit, still more typically between about 1650 andabout 1850 degrees Fahrenheit, or even higher, depending on theproperties that are desired. By adjusting the firing temperatures andtimes, the density and hardness as well as other properties of theresultant substrate 110 may be closely controlled.

As the mixture 127 reaches foaming temperatures, each mass of foaming140 glass, originating from one of the discrete rows or mounds, expandsuntil it comes into contact and fuses with its neighbors. The fused massof foaming glass then expands to conform to the shape of the walls ofthe mold 128, filling all of the corners. The shapes and sizes of theinitial mounds of mixture are determined with the anticipation that thefoaming 140 mixture 127 exactly fills the mold 128. After the glass isfoamed 140 to the desired density and pore structure, the temperature ofthe furnace is rapidly reduced to halt foaming 140 of the glass. Whenthe exterior of the foamed glass in the mold has rigidifiedsufficiently, the resultant body 110 of foamed glass is removed from themold 128 and is typically then air quenched to thermally shock the glassto produce a crazed microstructure 119. Once cooled, any skin or crustis typically cut off of the foamed glass substrate 110, which may thenbe cut or otherwise formed into a variety of desired shapes. Pore sizecan be carefully controlled within the range of about 5 mm to about 0.5mm, more typically within the range of between about 2.0 mm and 0.2 mm.Substrate density can be controlled from about 0.4 g/cc to about 0.26g/cc. Typically, the bulk density of the crushed foam may be as low as50% of the polyhedral density.

The substrate 110 may be either provided as a machined polyhedral shape110 or, more typically, as a continuous sheet that may be impactedand/or crushed to yield aggregate or pebbles 150 (typically sized to beless than 1 inch in diameter). The crushed substrate material 150 may beused to retain water and increase air volume in given soil combinations.The polyhedrally shaped substrate bodies 110 are typically sized andshaped as aggregate for use in an RSA composite material. The foamedglass material 110 itself is typically resistant to aqueous corrosionand has minimal impact on solution pH. In order to provide better pHcontrol, the foamed glass material 110 is typically doped (in batchstage, prior to foaming) with specific dicalcium phosphate or a like pHstabilizing material 124 which dissolves in water to help stabilize thepH. The foamed glass substrate 110 can typically hold between about 1.5and about 5 times its own weight in water in the plurality ofinterconnected pores 117.

Crushed foam bodies 150 may be rapidly made by an alternate method.Using soda-lime glass frit or powder as the glass component 122, theprocessing is similar to that described above but without the annealingstep. The alternate method employs the same foaming temperature rangesas related above. The batch material 127 consists of up to 8 percent bymass limestone, magnesite, or other applicable foaming agent 122,usually less than 2 percent by mass dicalcium phosphate 124, with thebalance being a borosilicate, silicate, borate or phosphate glass frit122. The batch 127 is then placed in a typically shallow mold 128, moretypically having a configuration of less than 2″ batch for every squareyard of mold surface. The mold 128 is typically then heated toapproximately 250° C. above the dilatometric softening point forsoda-lime glass (or the equivalent viscosity for other glasscompositions) and allowed to foam. The mold 128 is held at the foamingtemperature for less than 30 minutes and then pan quenched, i.e.substantially no annealing is allowed to occur

This method typically yields a material 110 of density less than 0.25g/cc, and more typically as low as about 0.03 g/cc. This material 110 isthen crushed into pebbles 150, with a corresponding lower bulk densityas per the above-described method. Material made by this alternatemethod has similar chemical properties as described above but hassubstantially lower strength.

Still another alternate method of preparing foamed glass substratematerial 110 is as follows. A batch 127 is prepared as discussed aboveand pressed into small (typically less than 5 mm diameter) pellets. Thepellets are rapidly heated, such as by passage through a flame source,passage through a rotary furnace, or the like. Typically, the pelletsare heated to about 1500 degrees Fahrenheit, such as to cause the pelletto expand as a foam particulate without the need for a mold. Thismaterial yields the weakest, but least dense foam particles. The typicaldensity may be as low as 0.02 g/cc or as high as 0.2 g/cc, or higher.

The foamed glass substrate 110 typically has a porosity in the range ofbetween about sixty-five and about eighty-five percent. Air holdingcapacity is typically between about forty and about fifty-five percent.

The pore size is typically between about 0.2 mm and about 2.0 mm indiameter, with a relatively tight pore size distribution. The finishedsubstrate 110 is typically processed through a series of conveyors andcrushing equipment to yield a desired size spread of pellets 150.

The precursor glass material is typically recycled or post-consumerwaste glass, such as plate, window and/or bottle glass. The glass isground or milled to a fine mesh profile of minus 107 microns. A typicalsieve analysis of the precursor glass is given as Table 1, and acompositional analysis of the glass is given as Table 2.

TABLE 1 Sieve Analysis Class up to Pass Remaindser Incidence (μm) (%)(%) (%) 0.7 1.3 98.7 1.3 0.9 1.6 98.4 0.3 1 1.8 98.2 0.2 1.4 2.8 97.21.0 1.7 3.7 96.3 0.9 2 4.6 95.4 0.9 2.6 6.4 93.6 1.8 3.2 7.9 92.1 1.5 49.9 90.1 2.0 5 12.0 88 2.1 6 14.0 86 2.0 8 17.5 82.5 3.5 10 20.5 79.53.0 12 23.3 76.7 2.8 15 27.3 72.7 4.0 18 31.1 68.9 3.8 23 37.2 62.8 6.130 45.1 54.9 7.9 36 51.2 48.8 6.1 45 59.2 40.8 8.0 56 67.6 32.4 8.4 6372.3 27.7 4.7 70 76.6 23.4 4.3 90 86.5 13.5 9.9 110 92.7 7.3 6.2 13597.1 2.9 4.4 165 99.3 0.7 2.2 210 100.0 0 0.7

TABLE 2 Glass oxide Wt. % SiO₂ 71.5 Na₂O 12.6 K₂O 0.81 Al₂O₃ 2.13 CaO10.1 MgO 2.3 TiO₂ 0.07 Fe₂O₃ 0.34 BaO 0.01 SO₃ 0.05 ZnO 0.01

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character. It is understood that theembodiments have been shown and described in the foregoing specificationin satisfaction of the best mode and enablement requirements. It isunderstood that one of ordinary skill in the art could readily make anigh-infinite number of insubstantial changes and modifications to theabove-described embodiments and that it would be impractical to attemptto describe all such embodiment variations in the present specification.Accordingly, it is understood that all changes and modifications thatcome within the spirit of the invention are desired to be protected.

1-21. (canceled)
 22. A method of slowing an aircraft overrunning arunway, comprising: a) paving an area with foamed vitreous bodies todefine a bed; b) covering the bed with a layer of cementitious materialto define a composite bed; and c) crushing at least a portion of thecomposite bed with an oncoming aircraft; wherein the composite bed is atleast 85 percent foamed vitreous bodies; and wherein the composite bedhas a cementitious surface wherein the foamed vitreous bodies have aclosed pore structure.
 23. The method of claim 22 wherein the compositebed is at least about 90 volume percent foamed vitreous bodies.
 24. Themethod of claim 22 wherein the foamed vitreous bodies are foamed glass.25. The method of claim 22 wherein the foamed vitreous bodies have acrush strength of between about 50 PSI and about 200 PSI.
 26. The methodof claim 221 wherein the foamed vitreous bodies have a crush strength ofat least about 100 PSI, and wherein the foamed vitreous bodies havedensities of between about 100 kg/m³ and 180 kg/m³.
 27. The method ofclaim 24 wherein the foamed glass bodies have compositions in the rangearound 70 weight percent SiO₂, around 13 weight percent Na₂O and around10 weight percent CaO with the remainder being other metal oxides. 28.The method of claim 22 and further comprising d) before step a), mixingthe foamed vitreous bodies with a cementitious material to define apaving mixture.
 29. The method of claim 22 wherein the bed is comprisedentirely of foamed vitreous bodies.
 30. The method of claim 22 whereinthe bed includes a cementitious matrix material in which the foamedvitreous bodies are distributed.
 31. A method of slowing an aircraftoverrunning a runway, comprising: a) establishing an aircraft arrestorbed adjacent a runway, wherein the aircraft arrestor bed is formed froma plurality of closed-cell foamed glass aggregate bodies covered by apaving layer; b) moving an aircraft over the aircraft arrestor bed; andc) crushing at least a portion of the arrestor bed with the aircraft;and d) slowing the oncoming aircraft; wherein the arrestor bed is has acrushing failure mode.
 32. The method of claim 31 wherein the arrestorbed is made up of at least about 90 volume percent foamed glassaggregate bodies.
 33. The method of claim 31 wherein the respectivefoamed glass bodies have a crush strength of between about 50 PSI andabout 200 PSI.
 34. The method of claim 31 wherein the respective foamedglass bodies have a crush strength of about 100 PSI, and wherein therespective foamed glass bodies have densities of between about 100 kg/m³and 180 kg/m³.
 35. The method of claim 31 wherein the paving layer is acementitious surface.
 36. The method of claim 31 wherein the arrestorbed has a contoured surface.
 37. A method of slowing an aircraftoverrunning a runway, comprising: a) establishing an aircraft arrestorbed adjacent a runway, wherein the aircraft arrestor bed is formed froma plurality of porous closed-cell foamed glass aggregate bodies coveredby a paving layer; b) piloting an oncoming aircraft onto the aircraftarrestor bed; c) removing kinetic energy from the oncoming aircraft bycrushing at least a portion of the arrestor bed under the weight of theoncoming aircraft; and d) stopping the oncoming aircraft; wherein thearrestor bed is has a crushing failure mode.
 38. The method of claim 37,wherein at least some of the plurality of foamed glass bodies aresuspended in a cementitious matrix to define a concrete.
 39. The methodof claim 37 wherein the paving layer is cementitious.
 40. The method ofclaim 37 wherein the arrestor bed is contoured.
 41. The method of claim37 wherein the foamed glass has a specific gravity of less than 0.3 anda median pore size ranging from 0.1 mm to 2.0 mm.